I'm O.K - A Murder Simulator is a computer game which was released as a free download by a group of people (proclaiming themselves to be "3 alcoholics and a foreign exchange student") calling themselves "Thompsonsoft".

This game was created and released in response to the "modest video game proposal" issued in late-2005 by activist attorney Jack Thompson, known for his crusades against sex and violence in entertainment, including computer and video games. This challenge dared computer game producers to release a game following a "script" he outlined, in which the grieving father of a child killed by a computer gamer takes vengeance by murdering many people connected with the gaming industry in a brutal manner. Thompson promised to contribute a $10,000 donation to the charity of choice of Paul Eibeler (the chairman of Take-Two Interactive, one of the game companies most heavily criticized by Thompson) if such a game were released. However, he has since claimed that the proposal was only a joke, and currently, no charity has been designated by Eibeler. The gaming-related webcomic site Penny Arcade has, however, made a $10,000 donation in Thompson's name to a charity set up by gaming companies to help sick children.

The "O.K" in the title refers to the initials of the protagonist, Osaki Kim. The reference to a "Murder Simulator" refers to what Thompson regularly proclaims all violent computer games to be.

I'm O.K is a side-scrolling game with 16-bit era low-resolution graphics that shares (to a degree) the basic gameplay (and somewhat lowbrow humor) of the Metal Slug series.

Thompson's letter describes a game whose protagonist is Osaki Kim, the father of a high school boy beaten to death with a baseball bat by a 14-year-old gamer who played a game about beating people to death with a bat. The game intro shows the court session where the killer is sentenced to "only" life in prison.

Osaki Kim then swears vengeance, and gets weapons, "even baseball bats. Especially baseball bats." Kim goes to New York to kill Paula Eibel, the CEO of "Take This", the company that made the "murder simulator on which his son's killer trained", along with her husband and kids, then urinates on their severed brain stems (as in Postal²). Kim then kills the lawyers of "Blank, Stare", the law firm that defended Take This, "with singer Jackson Browne's 1980's hit Lawyers in Love blaring." Kim then destroys high-tech video arcades called "GameWerks". Lastly, he goes to E³ on its opening at May 10, 2006, destroying all video game industry execs in "one final, monstrously delicious rampage".

Along the way, Kim steals supplies from Best Buy, Circuit City, Target and Wal-Mart stores, and roughes up store managers and clerks, yelling "'You should have checked kids' IDs!'"